Fixed some bugs

I was trying to use ofxFont for a project and Xcode was yelling at me: 

1. In ofTypesetter.cpp, the setFont method was setting `font` to itself, when it should be setting it to `_font`.
2. In ofFont.cpp, the overloaded drawCharTex method was trying drawing the text at position `unicode`, where I assumed you meant position.

DISCLAIMER: This is my first pull request and my first time using your library. Let me know if these fixes aren't valid for any reason. Thanks!